TRUST QA-4: Smoother exposedRefPrice in case of default

contracts/plugins/assets/AppreciatingFiatCollateral.sol

@@ -88,7 +88,7 @@ abstract contract AppreciatingFiatCollateral is FiatCollateral {
 
         // uint192(<) is equivalent to Fix.lt
         if (underlyingRefPerTok < exposedReferencePrice) {
-            exposedReferencePrice = hiddenReferencePrice;
+            exposedReferencePrice = underlyingRefPerTok;
             markStatus(CollateralStatus.DISABLED);
         } else if (hiddenReferencePrice > exposedReferencePrice) {
             exposedReferencePrice = hiddenReferencePrice;

contracts/plugins/assets/L2LSDCollateral.sol

@@ -53,7 +53,7 @@ abstract contract L2LSDCollateral is AppreciatingFiatCollateral {
 
             // uint192(<) is equivalent to Fix.lt
             if (underlyingRefPerTok < exposedReferencePrice) {
-                exposedReferencePrice = hiddenReferencePrice;
+                exposedReferencePrice = underlyingRefPerTok;
                 markStatus(CollateralStatus.DISABLED);
             } else if (hiddenReferencePrice > exposedReferencePrice) {
                 exposedReferencePrice = hiddenReferencePrice;

contracts/plugins/assets/compoundv3/CTokenV3Collateral.sol

@@ -77,7 +77,7 @@ contract CTokenV3Collateral is AppreciatingFiatCollateral {
 
         // uint192(<) is equivalent to Fix.lt
         if (underlyingRefPerTok < exposedReferencePrice) {
-            exposedReferencePrice = hiddenReferencePrice;
+            exposedReferencePrice = underlyingRefPerTok;
             markStatus(CollateralStatus.DISABLED);
         } else if (hiddenReferencePrice > exposedReferencePrice) {
             exposedReferencePrice = hiddenReferencePrice;

contracts/plugins/assets/curve/CurveStableCollateral.sol

@@ -88,7 +88,7 @@ contract CurveStableCollateral is AppreciatingFiatCollateral, PoolTokens {
 
         // uint192(<) is equivalent to Fix.lt
         if (underlyingRefPerTok < exposedReferencePrice) {
-            exposedReferencePrice = hiddenReferencePrice;
+            exposedReferencePrice = underlyingRefPerTok;
             markStatus(CollateralStatus.DISABLED);
         } else if (hiddenReferencePrice > exposedReferencePrice) {
             exposedReferencePrice = hiddenReferencePrice;

test/plugins/individual-collateral/collateralTests.ts

@@ -339,14 +339,29 @@ export default function fn<X extends CollateralFixtureContext>(
           })
 
           // Should remain SOUND after a 1% decrease
+          let refPerTok = await ctx.collateral.refPerTok()
           await reduceRefPerTok(ctx, 1) // 1% decrease
           await ctx.collateral.refresh()
           expect(await ctx.collateral.status()).to.equal(CollateralStatus.SOUND)
 
+          // refPerTok should be unchanged
+          expect(await ctx.collateral.refPerTok()).to.be.closeTo(
+            refPerTok,
+            refPerTok.div(bn('1e3'))
+          ) // within 1-part-in-1-thousand
+
           // Should become DISABLED if drops more than that
+          refPerTok = await ctx.collateral.refPerTok()
           await reduceRefPerTok(ctx, 1) // another 1% decrease
           await ctx.collateral.refresh()
           expect(await ctx.collateral.status()).to.equal(CollateralStatus.DISABLED)
+
+          // refPerTok should have fallen 1%
+          refPerTok = refPerTok.sub(refPerTok.div(100))
+          expect(await ctx.collateral.refPerTok()).to.be.closeTo(
+            refPerTok,
+            refPerTok.div(bn('1e3'))
+          ) // within 1-part-in-1-thousand
         })
 
         it('reverts if Chainlink feed reverts or runs out of gas, maintains status', async () => {

test/plugins/individual-collateral/compoundv3/CometTestSuite.test.ts

@@ -356,6 +356,7 @@ const collateralSpecificStatusTests = () => {
     })
 
     // Should remain SOUND after a 1% decrease
+    let refPerTok = await collateral.refPerTok()
     let currentExchangeRate = await wcusdcV3Mock.exchangeRate()
     await wcusdcV3Mock.setMockExchangeRate(
       true,
@@ -364,14 +365,22 @@ const collateralSpecificStatusTests = () => {
     await collateral.refresh()
     expect(await collateral.status()).to.equal(CollateralStatus.SOUND)
 
+    // refPerTok should be unchanged
+    expect(await collateral.refPerTok()).to.be.closeTo(refPerTok, refPerTok.div(bn('1e3'))) // within 1-part-in-1-thousand
+
     // Should become DISABLED if drops more than that
+    refPerTok = await collateral.refPerTok()
     currentExchangeRate = await wcusdcV3Mock.exchangeRate()
     await wcusdcV3Mock.setMockExchangeRate(
       true,
       currentExchangeRate.sub(currentExchangeRate.mul(1).div(100))
     )
     await collateral.refresh()
     expect(await collateral.status()).to.equal(CollateralStatus.DISABLED)
+
+    // refPerTok should have fallen 1%
+    refPerTok = refPerTok.sub(refPerTok.div(100))
+    expect(await collateral.refPerTok()).to.be.closeTo(refPerTok, refPerTok.div(bn('1e3'))) // within 1-part-in-1-thousand
   })
 }
 

test/plugins/individual-collateral/curve/collateralTests.ts

@@ -638,6 +638,7 @@ export default function fn<X extends CurveCollateralFixtureContext>(
           expect(await ctx.collateral.whenDefault()).to.equal(MAX_UINT48)
 
           // Decrease refPerTok by 1 part in a million
+          const refPerTok = await ctx.collateral.refPerTok()
           const currentExchangeRate = await ctx.curvePool.get_virtual_price()
           const newVirtualPrice = currentExchangeRate.sub(currentExchangeRate.div(bn('1e6')))
           await ctx.curvePool.setVirtualPrice(newVirtualPrice)
@@ -650,11 +651,17 @@ export default function fn<X extends CurveCollateralFixtureContext>(
           expect(await ctx.collateral.status()).to.equal(CollateralStatus.SOUND)
           expect(await ctx.collateral.whenDefault()).to.equal(MAX_UINT48)
 
+          // refPerTok should be unchanged
+          expect(await ctx.collateral.refPerTok()).to.equal(refPerTok)
+
           // One quanta more of decrease results in default
           await ctx.curvePool.setVirtualPrice(newVirtualPrice.sub(2)) // sub 2 to compenstate for rounding
           await expect(ctx.collateral.refresh()).to.emit(ctx.collateral, 'CollateralStatusChanged')
           expect(await ctx.collateral.status()).to.equal(CollateralStatus.DISABLED)
           expect(await ctx.collateral.whenDefault()).to.equal(await getLatestBlockTimestamp())
+
+          // refPerTok should have fallen exactly 2e-18
+          expect(await ctx.collateral.refPerTok()).to.equal(refPerTok.sub(2))
         })
 
         describe('collateral-specific tests', collateralSpecificStatusTests)

test/plugins/individual-collateral/frax-eth/SFrxEthTestSuite.test.ts

@@ -198,7 +198,7 @@ const collateralSpecificConstructorTests = () => {}
 
 // eslint-disable-next-line @typescript-eslint/no-empty-function
 const collateralSpecificStatusTests = () => {
-  it('does revenue hiding', async () => {
+  it('does revenue hiding correctly', async () => {
     const MockFactory = await ethers.getContractFactory('SfraxEthMock')
     const erc20 = (await MockFactory.deploy()) as SfraxEthMock
     let currentPPS = await (await ethers.getContractAt('IsfrxEth', SFRX_ETH)).pricePerShare()
@@ -215,14 +215,24 @@ const collateralSpecificStatusTests = () => {
     })
 
     // Should remain SOUND after a 1% decrease
-    await erc20.setPricePerShare(currentPPS.sub(currentPPS.div(100)))
+    let refPerTok = await collateral.refPerTok()
+    const newPPS = currentPPS.sub(currentPPS.div(100))
+    await erc20.setPricePerShare(newPPS)
     await collateral.refresh()
     expect(await collateral.status()).to.equal(CollateralStatus.SOUND)
 
-    // Should become DISABLED if drops more than that
-    await erc20.setPricePerShare(currentPPS.sub(currentPPS.div(99)))
+    // refPerTok should be unchanged
+    expect(await collateral.refPerTok()).to.be.closeTo(refPerTok, refPerTok.div(bn('1e3'))) // within 1-part-in-1-thousand
+
+    // Should become DISABLED if drops another 1%
+    refPerTok = await collateral.refPerTok()
+    await erc20.setPricePerShare(newPPS.sub(newPPS.div(100)))
     await collateral.refresh()
     expect(await collateral.status()).to.equal(CollateralStatus.DISABLED)
+
+    // refPerTok should have fallen 1%
+    refPerTok = refPerTok.sub(refPerTok.div(100))
+    expect(await collateral.refPerTok()).to.be.closeTo(refPerTok, refPerTok.div(bn('1e3'))) // within 1-part-in-1-thousand
   })
 }